Monday, January 1, 2024

Phil 417 - The Metaphysics of Time

Questions on the Ontology of Time

Henry Molaison suffered seizures from his youth until his twenties. In an attempt to cure him of the worsening seizures, his parents took him to numerous doctors, including a neurosurgeon named William Scoville. At the age of 27, Henry underwent an experimental operation to remove parts of his brain. His seizures significantly decreased in temperament and frequency, but at a high cost – he lost the ability to recall and would be stuck in the present moment for the rest of his life (Corkin, 2013). To ponder what it must be like to have no ability to recall would be to ponder what life might be like if one had no concept of time. While Henry would physically change, to him, his life experience would be perpetually stuck in the present moment. For the average person, however, the ability to remember allows her to seemingly experience time and with it the perception that it flows and passes.

Philosophical conversation on time has existed as long as the dialogue of philosophy itself. Some have argued that time flows, while others argue it is a static structure and is not real. Questions relating to the ontology of time are: does it flow, or does it follow some other construct? Do things exist only in the present or can they exist in the future and past? Many philosophers have pondered these questions and have advanced theories to explain time. This paper will review and explain the earliest debates on these questions between Heraclitus and Parmenides to show the long-standing nature of this examination (Bardon & Dyke (Eds.), 2013).  It will then review modern perceptions of time concerning A-Theory and B-Theory as explained by J.M.E McTaggart and how these ideas relate to the ideas of Presentism, Growing Block Theory and Moving Spotlight Theory (A-Theories) and Eternalism (B-Theory) (Markosian, 2002 and Bardon & Dyke (Eds.), 2013).

Ancient Discussions on Time


Flux is a Heraclitan idea. One of his fragments claims all existence is in a constant state of change and that a person cannot step in the same river twice (Graham, 2019). At first glance, the idea of not being able to step into the same river twice is confusing. When a person steps into a stream of water in the morning while on a hike, and then crosses that same stream again, in his mind, he is stepping into the same thing. However, Heraclitus is being more specific in saying that the creek and the water molecules and the way the water flows and the minerals the water molecules have acquired (Bardon & Dyke (Eds.), 2013) – all of those features of the creek have changed between the first time the hiker stepped in it and the second time he crossed it. Precisely speaking, the creek is not the same from one moment to the next.

With this focus on flux and constant change, Heraclitus further noticed that despite the perpetual variation, things seemingly remained constant through cycles. However, he is unambiguous in noting that things do change from one moment to the next and this marking of change denotes time passed. Stated differently, Heraclitus noted the flux of everything both is and is not. This flux of things, if observed long enough, turns out to be opposites: day and night, winter and summer, war and peace, and satiety and hunger (2013, p. 13). In brief, Heraclitus would claim what was past existed and was real, and it changes to the present which also exists and is real and eventually things change again and still be real.


Parmenides took a different tact regarding the explanation of reality and refused to embrace the idea of flux – that existence both is and is not. Rather, he believed that everything just is. He explained this by way of a poem, in which a mortal meets a goddess, and she explains to the mortal the way of truth. She explains that there is one route called “it is” and there is another route called “it is not” and there is even a third route called “it is, and it is not” (2013, p. 17). The second and third routes are dead ends, and there is only one route: it is. This reality of existence does not change, for change is simply the mortal’s perspective. Furthermore, how can something which exists, not exist? This is contradictory and mortals are “deaf and blind at once” (Palmer, 2016) for not admitting and comprehending this contradiction. Parmenides simply concludes there is no flux, but everything simply exists and is the One. To Parmenides, Heraclitus would have been on the second route and his ideas would be contradictory. And since flux does not exist, the passage of time also does not exist and therefore time does not exist – it is simply human misunderstanding.

The philosophical discourse between Heraclitus and Parmenides continues to this day. The manner of looking at reality and time splits into differing factions of thought.

Modern Discussions on Time

Many theories regarding the metaphysics of time fall under two camps: A-Theory and B-Theory. These two theories stem from the philosopher J.M.E. McTaggart who noted two types of series in time and then argued that time does not exist (McDaniel, 2009). In one series, events can be ordered earlier than or later than one event in relation to another; he called these B-series. He also described a second series of events in which one event is noted as the present moment, and this event changes, first by being future, then being present, then being past, as it moves position in a series; he called these events the A-series.

From these two types of series emerge notions of A-Theory and B-Theory. In brief, A-Theory ideas contend time is real, especially the present moment, and that all time is viewed as either past, present, or future. (Bardon & Dyke (Eds.), 2013). However, B-Theory ideas argue that time is not real and that events simply have relations that are either earlier-than or later-than (2013). In a review of the theories of time, one podcaster explained the key difference between the two theories as being the determination of the present either being real (A-Theory) or the present not being real (B-Theory) (Macherla). Also, while A-Theory is committed to the idea of time being linear or growing, B-Theory contends there is simply existence and things only occupy a particular space-time coordinate.

A-Theories: Presentism, Growing Block, and Moving Spotlight

Most peoples’ paradigm of time aligns with A-Theory ideas. Three of these theories are Presentism, Growing Block, and Moving Spotlight. Before describing each one, it may be helpful to frame the idea of time as a block of cheese, and the present moment is represented as a slice of cheese from the block.

In the theory of Presentism, the only thing that is real is the present, viewed as a slice of cheese. Whatever exists now is real, but nothing in the past or future is considered real and therefore, the past and the future do not exist (Markosian, 2002). A comprehensive list of things that exist in the present moment could be produced, but nothing from the past, such as dinosaurs, or nothing from the future, such as a time machine, would be on that list of things in the present, therefore dinosaurs and time machines do not exist and are not real.

In the Growing Block theory, only the past and the present are real, but the future does not exist (2002). An observer might strongly contend that things in the past were just as real as the present. Therefore, time is like a growing block of cheese, where the present moment is the slice of cheese that grows and acts as the edge of time. The future, however, is beyond the block and does not exist.

Lastly is the Moving Spotlight theory, named by C.D. Broad (2002), contends that all past, present, and future are real, but differs from the B-Theory in contending that time exists, and the present is not only real, but also unique since there is a metaphorical light on the present moment. This light constantly moves and illuminates the present, hence there is a sense of flow. All time is laid out, but light only shines on the present moment.

B-Theory: Eternalism

Continuing with the block of cheese example for explaining time, the B-Theory of Eternalism contends that all moments in time equally exist and that the past, present, and future are not real (2002), and all that exists is the block of cheese. The universe simply exists in all time and space, and things only occupy some space-time coordinate. Indeed, things may serially exist before another thing much like page 7 exists at a space-time coordinate which simply precedes page 8 which exists at an adjacent space-time coordinate, but all pages equally exist – there is nothing unique about page 7.

Discussion on Time

While I find the practical nature of time useful, such as being prompt to a meeting or having the ability to recall the anniversary date of my marriage, nevertheless, it is odd that we spend a lot of thought on this subject. By way of relation, I wonder why we don’t spend as much effort on discussing the nature of a kilometer, meter, or centimeter. After all, isn’t time simply an attempt at keeping the score on a change?

After having the opportunity to research and write this essay, I realize I fall in the B-Theory camp and align my views with those of Spinoza. In reviewing Spinoza’s ideas on the metaphysics of time, Waller (2012) offers a clear analogy to explain why the B-Theory makes better sense. Suppose Bob completes the paperwork for a loan at 10:30am and then signs the loan at 10:31am and shakes the hand of the loan officer. However, at 10:35am when Bob receives the loan check, he claims he is not the same Bob who signed the form – that Bob is past Bob, while this Bob is present Bob. This way of thinking is incoherent!  Bob is Bob whether in the past, present, or future. To return to the block of cheese analogy, indeed slices do exist (Bob being a different slice at different times), but a clearer way of comprehending the entirety of the idea is to admit all the slices are the same cheese.


In conclusion, the age-old philosophical discourse on time centers around whether it flows or is static. From Heraclitus and Parmenides to moderns such as McTaggart and Broad, this debate continues today under A-Theory and B-Theory ideas. A-Theory ideas claim time is real to varying degrees, but B-Theory ideas claim time is not real and that there is only existence.


Bardon, A., & Dyke, H. (Eds.). (2013). A companion to the philosophy of time. John Wiley & Sons, Incorporated.

Corkin, S. (2013). Permanent present tense: The unforgettable life of the amnesic patient, h. m.. Basic Books.

Graham, D. W. (2019, September 3). Heraclitus (Stanford Encyclopedia of Philosophy). 

Markosian, N. (2002, November 25). Time (Stanford Encyclopedia of Philosophy).

Macherla, R. (2021, March 21). Philosophy of Time. In The Human Condition. Spotify for Podcasters.

McDaniel, K. (2009). John M. E. McTaggart (Stanford Encyclopedia of Philosophy). 

Palmer, J. (2016). Parmenides (Stanford Encyclopedia of Philosophy). 

Waller, J. (2012). Persistence through time in Spinoza. Lexington Books/Fortress Academic.

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